An aromatic carboxylic acid or a derivative thereof (for example, an ester of an aromatic carboxylic acid, and an aromatic carboxylic anhydride) is used as a raw material for various resins and is in great demand all over the world. For example, terephthalic acid, which is derived from p-xylene, has been used as a raw material for a general-purpose polyethylene terephthalate) (PET) resin all over the world. Moreover, pyromellitic anhydride, which is derived from durene, has been widely used for various purposes such as an electronic material.
Currently, most of the aromatic carboxylic acids or derivatives thereof are produced by oxygen-oxidizing (or aerobically oxidizing) a corresponding aromatic compound. For example, a carboxylic acid (e.g., terephthalic acid) is produced by an air oxidation method using a catalyst system containing a transition metal salt and bromine. Such a method, however, has some problems, for example, the necessity of a relatively high reaction temperature or the corrosion of an apparatus by a halogen-containing catalyst.
Thus a method for carrying out a relatively efficient reaction under a relatively mild condition has been examined. For example, Japanese Patent Application Laid-Open No. 354596/2001 (JP-2001-354596A, Patent Document 1) discloses that, for producing an organic compound using an imide catalyst, a successive addition of the imide catalyst to a reaction system improves the conversion of a substrate and/or the selectivity of an object compound. However, this process is basically conducted on the premise that the reaction is carried out in the presence of a solvent, and the purification efficiency is low. Moreover, Japanese Patent Application Laid-Open No. 331242/2002 (JP-2002-331242A, Patent Document 2) discloses that use of a highly fat-soluble imide catalyst allows efficient oxidation of cyclohexane or the like in the absence of a solvent or even in a reaction solvent having a small polarity. However, there still remains an insufficient catalyst activity or an insufficient yield of the product for such conventional processes. In addition, there is much room for an effort for a reduction in the cost. Therefore, the production process is required to produce the object compound at a high selectivity and a high yield by allowing the reaction to proceed efficiently in the presence of a relatively small amount of a catalyst, and to have an improved purification efficiency.